Cosmos sulphureus

RHS Plant Profile
yellow cosmos

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yellow cosmos RHS
yellow cosmos RHS
yellow cosmos RHS

Synonyms

Bidens sulphurea

Plants for pollinators
Annual Biennial

A half-hardy annual with fresh, fern-like foliage and a long flowering season. Selections are variable in height, most between 50cm and 1m, but including some dwarf forms. Flower colour is varied, in many tones of yellow, orange and red

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
1 year
Max Spread
0.1-0.5 metres
Max Height
0.1-0.5 metres

Growing Conditions

Chalk Loam Sand
Moisture
Moist but well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
West–facing or South–facing
Exposure
Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H3

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Bushy, Columnar upright
Genus
Cosmos can be annuals or perennials with simple or pinnately divided leaves and large, long-stalked daisy-like flowers in summer
Name Status
Correct
Plant Range
Mexico, C America, N S America

How to Grow

Cultivation

Grow in moderately fertile, moist but well-drained soil in full sun

Propagation

See sowing seeds indoors

Suggested planting locations and garden types

  • Cottage and informal garden
  • City and courtyard gardens
  • Patio and container plants
  • Wildlife gardens
  • Coastal
  • Cut flowers
  • Flower borders and beds

Pruning

Deadheading should be carried out regularly to prolong flowering

Pests

Aphids and slugs may be a nuisance

Diseases

Grey moulds may be a problem